In the field of hydrocarbon exploration and extraction, it is sometimes necessary to drill a relief well to provide a conduit for injecting a fluid, such as mud or cement, into a target well. Such procedures most often occur when the relief well is drilled to kill the target well. A relief well is typically drilled as a straight hole down to a planned kickoff point, where it is turned toward the target well using conventional directional drilling technology. Drilling is thereafter continued until the relief well intersects the target well, thereby establishing hydraulic communication between the two wells. Owing to the difficulty in intersecting the relief well with the target well, the relief well may be drilled at an incident angle to the target well rather than simply intersecting the target well perpendicularly.
Establishing the conduit between the relief well and the target well can be difficult due to having to drill through a section of cement and casing surrounding the target well. In some instances, the relief well is drilled so that it approaches close proximity to the target well (e.g., within 0.2-0.5 meters) but does not make contact with the target well. At this point, a system designed for establishing hydraulic communication between the two wells may be lowered through the relief well until it is in position near the target well at the closest approach. Once in place, the system can be actuated to establish hydraulic communication between the wells.
In any event, once hydraulic communication is established, the relief well may function to relieve pressure from the target well. In some instances, fluid from the relief well U-tubes into the target well. Pumps are used to keep the annulus of the relief well full, followed by pumping at the appropriate kill rates until the blowout is dead.